Cysts are very common in the scalp. They do feel hard and immovable. They can stay forever and not cause a problem but sometimes the encapsulated infection (this is what a cyst is) is able to "get out" so to speak and cause an infection of your scalp. I have been there and what pain that was. I couldn't even move my head. So if you have not had them checked out, make an appointment with a dermatologist just to be sure especially since one of them is tender.
listen do not mess with that, I had a friend who had one the size of a golf ball. best get it checked cld be anything from a Tick,bug. to a small tumor. dont sit and ask about it .please go. to ur Er